Xi’an, China
Xi’an, China

Time filter

Source Type

Guo F.,AFEU | Guo J.,AFEU | Zheng W.,AFEU | Qi Y.,AFEU
Proceedings of the 2014 International Symposium on Information Technology, ISIT 2014 | Year: 2015

Aiming at the drawback of the partial-band jamming degrade the FH communications, a cognitive frequency hopping (CFH) system model that combine the cognitive radio with the FH is proposed. The performance of the system under the partial-band jamming is analyzed and the closed-form error probability expression is given. The performance of partial-band jamming resistance in CFH communications and common FH communications are simulated and compared. The theoretic analysis and simulation results show that under the condition of ideal synchronization the CFH can avoid the jamming spectrum, and adjust the hopping frequency dynamically in a clean spectrum hole. Compare with the normal FH communications, the CFH communications have the better performance of jamming resistance. © 2015 Taylor & Francis Group, London.

Hao L.,AFEU | Zhang Y.-S.,AFEU | Li Z.,AFEU | Xu J.,Unit 93617 of PLA
Advanced Materials Research | Year: 2014

For the issue of MIMO airborne radar clutter modeling in different environment conditions, a clutter modeling method based on composite model is proposed. It builds different types of clutter model through the changes of model parameters. The clutter model consists of clutter amplitude distribution model, and clutter cell scattering model. After considering the error factors such as element error, channel error, clutter fluctuation, a clutter modeling method based on composite model under error conditions is proposed. Finally, the computer simulation is made about the amplitude, the back-scatter coefficient, error factors, the space-time MV spectrum and the characteristic spectrum of different types of clutter through changing the model parameters. The simulation results show that: In ideal conditions, the Clutter Spectrum has good space-time characteristic, but in error conditions, the clutter fluctuates tempestuously, and in different environment conditions the fluctuation degree is different. © (2014) Trans Tech Publications, Switzerland.

He J.,Institute of Telecommunication Engineering | Zhang Q.,Institute of Telecommunication Engineering | Zhang Q.,Fudan University | Yang X.-Y.,Institute of Telecommunication Engineering | And 3 more authors.
Yuhang Xuebao/Journal of Astronautics | Year: 2011

Synthetic aperture LADAR (SAL) is an active laser imaging system. It has much higher imaging resolution than the microwave synthetic aperture radar, and can realize the refined imaging for a far distance target. Due to the extra large bandwidth of laser signal, the hardware of SAL is difficult to satisfy the requirement for Nyquist sampling rate. A new signal sampling method based on the compressed sensing (CS) theory is proposed to reduce the sampling rate of echoes in this paper. In the method, the echoes are randomly sampled by using an optical heterodyne process, and then the high-resolution range profile is recovered by using the orthogonal matching pursuit algorithm (OMP). The 2-D image is recovered by using frequency scaling algorithm. Simulations demonstrate that high-quality images can be reconstructed even though the sampling rate is much lower than the Nyquist sampling rate.

Lei L.,AFEU | Xiao-dan W.,AFEU | Xi L.,The Computer College | Ya-fei S.,AFEU
Pattern Analysis and Applications | Year: 2015

Error-correcting output codes (ECOC) can effectively reduce the multiclass to the binary and is attracting close attention, in which the construction of coding matrix based on data is the key to use ECOC to solve multiclass problems. An approach to the hierarchical error-correcting output codes based on support vector data description is presented in this paper. The main idea of the work is to construct the data-driven coding matrix with the help of support vector data description and binary tree. The support vector data description is used to measure the class separability quantitatively to obtain the inter-class separability matrix. And, a binary tree is built based on the matrixes from bottom to top. Then, each node of each layer is encoded to get the final hierarchical error-correcting output code. The independence of base classifiers trained by different encoding methods is compared in experiments. The results show that the proposed technique can promote the diversity of the base classifiers and enhance the classification accuracy. © 2015 Springer-Verlag London

Deng D.H.,Institute of Telecommunication Engineering | He J.,Institute of Telecommunication Engineering | Wang M.,Institute of Telecommunication Engineering | Zhang Q.,Institute of Telecommunication Engineering | Bai P.,AFEU
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

If the target or any structure on the target undergoes micro-motion dynamics, such as mechanical vibrations or rotations, it will induce Doppler frequency modulation on the returned signal that generates sidebands about the target's Doppler frequency, which is referred to as the micro-Doppler effect. The micro-Doppler signatures enable certain properties of the target to be determined that may be used for target recognition. In this paper, taking the Micro-Doppler effect caused by the rotation of target in Bi-static inverse synthetic aperture radar (Bi-ISAR) system as example, a novel extraction method of the micro-motion feature is presented. With the proposed method, the micro-motion parameters of the target can be detected rapidly from the spectrogram and the computational efficiency can be enhanced compared with that of the modified extended Hough transform. A computer simulation is given to illustrate the effectiveness of the proposed method. © 2011 IEEE.

Loading AFEU collaborators
Loading AFEU collaborators